Gas turbine engines are known to include a compressor section for supplying a flow of compressed combustion air, a combustor section for burning fuel in the compressed combustion air, and a turbine section for extracting thermal energy from the combustion air and converting that energy into mechanical energy in the form of a rotating shaft.
Modern high efficiency combustion turbines have firing temperatures that exceed about 2,700° F., and even higher firing temperatures are expected as the demand for more efficient engines continues. Many components that form the “hot gas path” combustor and turbine sections are directly exposed to aggressive hot combustion gasses, for example, the combustor liner, the transition duct between the combustor and turbine sections, and the turbine stationary vanes and rotating blades and surrounding ring segments. In addition to thermal stresses, these and other components are also exposed to mechanical stresses and loads that further wear on the components. Other turbine components, such as electronic and mechanical controllers, fuel metering equipment, auxiliaries, load packages including generators and exciters, and valves similarly receive in-service wear.
It is known to perform detailed periodic scheduled maintenance of turbine components based upon benchmark manufacturer recommendations developed from engineered design parameters in view of anticipated turbine operation conditions. However, a shortcoming of this methodology is that actual turbine operating conditions often appreciably differ from the anticipated turbine operating conditions due to intentional (e.g. running the turbine at higher combustion temperatures) or unintentional (e.g. non-optimal shutdowns, trips, fast cool downs, water washing, and fuel nozzle water purges) reasons. Thus, the components commonly experience temperatures, cycles, loads, stresses, strains, etc. that are greater or less than for which they were designed. Accordingly, Type I and II errors occur in connection with the periodic scheduled maintenance, that is, maintenance is performed when the turbine components are fine (Type I) and maintenance is not performed when the turbine components need to be repaired, refurbished or replaced (Type II).
Several approaches have been taken to address this shortcoming. One approach involves developing less expensive and time consuming inspection and maintenance procedures, such as non-destructive and in-operation examination of the turbine components, for example those described in U.S. Pat. Nos. 4,746,858 and 5,140,528. Another approach involves creating individualized maintenance schedules uniquely associated with and based on the actual operating history of a particular turbine, for example that described in U.S. Pat. No. 6,343,251.
If a unique individual turbine maintenance schedule is created, a problem arises if an individual turbine component is used on more than one turbine. Another problem arises if a component type (e.g. row 1 blade) is not identical with another similar component type (e.g. row 1 blade), for example, if one row 1 blade was manufactured with one type of ceramic thermal barrier coating and another row 1 blade was manufactured with another type of ceramic thermal barrier coating, this difference is not addressed. Another problem arises if some individual component types are repaired or replaced while other individual component types are not repaired or replaced within the turbine. Oftentimes, some components are replaced that still have serviceable life in them to “reset” the clock on the repair cycle.
Accordingly, there is a need for additional approaches to reduce maintenance costs and improve upon the prior art.